Burners are well known, for example in furnaces, dryers, kiln or boilers. Typically burners have an air duct which ducts an air stream into a combustion chamber, and include one or more fuel injectors which inject fuel into the air stream and into the combustion chamber, where continuous combustion occurs. An example of a fuel injector is described in US Patent Application No. 2004/0234912 by Sarv et al. This fuel injector has a nozzle which injects fuel in a substantially conical spray.
Some existing fuel injectors provide a flame which is unstable. Such flames are known to cyclically change dimensions as the flame “catches up” with the supplied air and fuel. Unstable flames are prone to flameouts. If a flameout arises, fuel leaks into the combustion chamber. Some combustion chambers include flameout detectors to stop fuel supply in the event of a flameout. Lowering the risks of flameout is thus one of the main goals in the design of a burner.
Another one of the main goals in the art is to reduce combustion by-products. Regions of high temperature concentrations within a flame, known as hotspots, are known to generate by-products such as nitrogen oxides (NOx). Optimizing the temperature distribution in the flame to avoid hotspots is thus another goal in the design of a burner or its fuel injector.